Airplane-propeller.



L. Sa-BARR.

AIRPLANE PROPELLER.

-APPL'ICAT|0N FILED MAXI8.'I9I8.

Patentmi Apr. 15, 1919.-

' snares AIRPLANE-PROPELLER.

Specification of Letters Patent.

Patented Apr. 15, 1919.

Application filed May 18, 1918. Serial No. 235,287.

To all whom it may concern:

Be it known that I, LESTER S. BARR, a citizen of the United States, andresiding at Washington, District of Columbia, have in vented certain newand useful Improvements in Airplane-Propellers, of which the followingis a, specification.

1 The present invention relates to propellers and more particularly tothe type adapted for use in tractor airplanes, that is the type ofpropeller which is located at the front of the airplane. It is welllmown that the hub and the portion of the blades joining the hub afi'ordsurfaces which resist the movement of the airplane. In someconstructions, in order to reduce this resistance, a conical orconvexedly curved cap has been mounted in front of the central part ofthe propeller, the surface of the cap forming a stream line with thefuselage. In none of the present machines, as far as I am aware,'has anyprovision been made to put the head resistance mentioned above, to anyuseful purpose.

' It is the principal object of this invention to provide a propellerwhich will utilize the head pressure at the hub and adjacent thereto toaid in turning the propeller; will auto-' matically conduct away the airstriking the central part of the propeller so that it does not impingeon-the fuselage and retard the plane, and furthermore will produce areduced pressure at the center of the propeller thereby augmenting theforce turning the same. Other objects and features of novelty will beapparent from the description taken in connection with the drawings inwhich:

Figure 1 isa front elevation-of a propeller constructed inaccordancewith the present invention; and

Fig. 2 is a section taken substantially on the line 22 of Fig. 1.

Airplane propellers in general use at present are made of wood and haverelatively large hubs, first because of the type of fastening employedto secure the propeller to the propeller shaft and second because thestresses are greatest at the hub, these stresses including that due tothe centrifugal pull of the blades and the cantaliver action of eachblade. According to my invention, however, the diameter of the hub forsecuring the propeller to its shaft is relatively small, and aconstruction is provided just outside the hub which utilizes the impactor deflection of the air due to the velocity of the airplane to aid inturning the propeller.

Referring to the drawings the reference numeral 10 indicates the hub ofthe propeller which may be formed with the tapered bore 11 and thekey-ways 12 for the purpose of mounting the propeller on its shaft. Itis to be observed that the hub is relatively small compared to the usualairplane propeller construction. Preferably the propeller is made frommetal and is one integral piece, although the invention is not limitedto this material nor to the integral structure. Spaced from he hub 10and concentric therewith is a ring 13. The rear edges of the ring andhub are connected by a walll l thereby forming an annular chamber 15between said parts. At the front ends of the hub and ring are the blades16 which are interposed and secured to said parts and constructed andarranged to utilize the impact and deflection of the air to aid inturning the propeller. Furthermore these blades act as reinforcingmembers between the ring and hub. They also give the air 'a circularmotion within the chamber for a purpose presently to be mentioned. Theparts thus far described in effect constitute a spider which correspondsto the hub in the usual propeller construction.

Secured to the outside of the ring 13 are the main blades 17 which areof the usual form. Each of these blades is formed with a radial airpassage 18 which extends from the annular chamber 15 to adjacent the tipof the blade the passage opening at the trailing edge 19 thereof. Asshown in Fig. 2 the inner ends 20 of these passages are flared out orfunnel shaped so as to provide a better entrance for the air.

In the operation of the propeller the main blades 17 of course drive theplane in the usual way. The air striking the central portion of thepropeller however impinges on i the blades 16 and thereby aids, due tothe impact and deflection of the air, in turning the propeller. Becauseof the inclination of the blades 16. the air after it leaves the same isgiven a circular motion in the chamber 15 thereby conducting it to thepassages 19. Thus. the passages 19 relieve the chamber 15 from anyaccumulation of air. Furthermore although these passages are relativelysmall compared to the chamber locity imparted to the air in the saidpas- I sages is considerable, due to the centrifugal force generated inthe air by the rotation of A the propeller blades. Thus the main bladeswith the passages therein act as an exhauster to reduce the pressure ofair in chamber 15, thereby adding to the pulling power of the propeller.It will be observed further that the discharge of air at the edge 19 ofthe blades tends to offset the reduction of pressure at the trailingedges thereof and consequently tends to reduce the retarding efiect ofthis reduction of pressure. The spider construction which is used forconnecting the main blades to the tively light, is sufliciently strongto withstand the forces to which it is subjected and yet permitembodying in its construction the features mentioned above. I

Although a specific embodiment of the inventionhas been described it isto be understood that it is not limited to the exact form shaft,although relaing a central hub, a concentric ring spaced from the hub,a-wall joining the rear ends of the hub and ring thereby forming anannular chamber open at the front of the propeller, blades secured tosaid ring each blade having an air passage formed therein ex tendingfrom said chamber to the'end of the blade and having i tsouter openingat the trailing edge of! the blade, and blades connecting the front endsof the hub and ring constructed and arranged to effect a circular motionof the air entering the chamber to direct the same to the -inner endsof-said passages, said blades members. v

' In testimony whereof I afiix my signature.

LESTER S. BARR.

alsoa'cting as reinforcing

